<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let year = prompt('请输入年份：')
        if(year % 400 === 0 || year % 4 ===0 && year % 100 === 1){
             alert('今年是闰年')
         }
        else{
             alert('今年是平年')
         }
    </script>
</body>
</html>